The Invention is based on a wiper arm for windshield wiper.
Known windshield wipers have a wiper arm that comprises a mounting part and an articulated partxe2x80x94with a wiper barxe2x80x94hinge-mounted on it. A wiper blade is hinge-mounted on this, which wiper blade is constructed out of a carrier strap system having a primary middle strap and secondary, intermediate straps connected in hinged fashion, as well as claw strips, and a wiper strip. Simple systems have only one middle strap, on which the claws are provided.
On its end facing the mounting part, the articulated part comprises a spring chamber. The spring chamber is open toward the window and has an extension designed in the shape of a slot toward the wiper bar with a crossbar to which a retaining clip of the tension spring is attached. A C-bracket is arranged on the other end of the tension spring, which is attached to an attachment device of the mounting part. The articulated part can thereby rest against a bolt-shaped articulated axle of the mounting part via an open hub. A wiper arm is made known in DE 37 09 994 A1 in which the open hub is provided on the mounting part, and the articulated axle is provided on the articulated part. The joint formed in this fashionxe2x80x94also referred to as a hinged jointxe2x80x94and the attachment device of the tension spring are arranged in relation to each other in such a fashion that the tension spring pulls the articulated part and the wiper bar in the direction of a front window or rear window of a vehicle. The wiper blade therefore lies against the vehicle window under the force of the tension spring and is limited in the working position by this.
The articulated part of the windshield wiper can be swung away from the vehicle window to clean or install the wiper blade. To accomplish this, the articulated part is swivelled around the hinged joint so far that the resultant line of force of the tension spring exceeds the articulated axle toward the outside, and the tension spring pulls the articulated axle against a stop on the mounting part in a swung-out position. In order to achieve a secure lock in the swung-out positionxe2x80x94which makes installation easy without the articulated part with the wiper bar slamming back against the vehicle windowxe2x80x94the articulated part must be rotated fairly far around the articulated axle, and the wiper bar must be moved far away from the vehicle window. If, in undesired fashion, the wiper bar leaves the swung-out position and slams against the vehicle window before installation of the wiper blade is complete, the vehicle window or the wiper arm can be damaged.
In the preassembled state, in the delivered position, the hinged joint is held together by a preload of the tension spring. Bearing surfaces are provided on the mounting part and the articulated part for this purpose, which support the hinged joint on the side opposite to the hub in relation to the line of application of the tension spring. A statically stable position of these parts is given when the line of force of the tension spring extends between the support points on the articulated axle and on the bearing surfaces. As a result of a slight effect of force on the preassembled wiper arm, e.g., caused by shaking during transport or careless handling, the bearing surfaces can mutually shift and slide off of each other, so that the articulated axle slips out of the hub, and the hinged joint falls apart into its individual components. Additional assembly work is required as a result, and there is a risk that parts will become lost.
According to the invention, the bearing surfaces are arranged and/or designed in such a fashion that, with a smaller joint angle xcfx86 beyond the transport position, the articulated axle moves from its seating surface in the hub toward the open end, thereby increasing the preload of the tension spring. Advantageously, one bearing surface on the mounting part or on the articulated part is concave in each case, while the other bearing surface on the other part is designed correspondingly convex in each case. The concave bearing surface thereby comprises a lobe designed in the shape of a cam toward the outside in relation to the line of force of the tension spring. The bearing surfaces designed in this fashion secure a defined position of the parts named above in the preassembled state of the wiper arm in that they form a type of spring detent. If transverse forces or a torque that has the tendency to decrease the joint angle xcfx86 beyond the transport position act on the parts as a result of shaking or a bump, the convex bearing surfacexe2x80x94guided by the joint bolt in the open hubxe2x80x94slides along the lobe designed in the shape of a cam, and the distance between the attachment devices of the tension spring increase as a result and, as a consequence, the preload of the spring increases. After the stress, the parts are returned to their starting positionxe2x80x94with elimination of part of the preloadxe2x80x94so that they cannot continue to come loose during repeated shaking or bumping, in that they slide off of each other bit by bit.
For easier installation, a starting ramp is formed as part of the lobe toward the outside, via which the convex bearing surface can be easily guided over the cam-shaped lobe into the concave bearing surface. Basically, the bearing surfaces can be provided at a random location of the mounting part or the articulated part. The object of the invention can be attained particularly simply when the contour of the attachment device of the tension spring on the mounting part is designed cylindrical in shape toward the articulated part and serves as a bearing surface.
According to an embodiment of the invention, the articulated partxe2x80x94when moved into a swung-out position with a joint angle xcfx86 greater than 180xc2x0xe2x80x94reaches a stop for seating and rests against it. Moreover, a latching cam with a latching recess abuts the concave bearing surface on the other side of the hub toward the open end, into which latching recess the convex bearing surface snaps in the swung-out position. The latching cam is arranged toward the stop in such a fashion that the articulated axle is displaced in the swung-out position by a displacement length toward the open end of the hub, and the line of force of the tension spring extends between the stop and the latching recess. In the swung-out position, the articulated part therefore rests against the stop and the latching cam, the position of which can be freely selected, so that a random swung-out angle is achieved and can be harmonized with the circumstances of the vehicle.
The latching cam can be eliminated if, according to a further embodiment of the invention, the stop for limiting the swung-out angle is designed as a spring detent, and the tension spring serves as a stop spring. Advantageously, the spring detent has a convex latching element that is arranged on the mounting part or on the articulated part and, in the swung-out position of the articulated part, snaps into a latching recess on the other part in each case, and, during the process of snapping into place, the articulated axle comes slightly loose from its seating in the open hub, and the preload on the tension spring increases. The articulated part with the wiper bar is therefore held securely in a swung-out position with a small swung-out angle.